1. Field of the Invention
The present invention relates to diversity techniques and, more specifically, to a diversity combining technique for use in a multi-level digital-modulated signal receiver such as a 4-ary FSK (frequency Shift Keying) receiver.
2. Description of the Related Art
There have been proposed several diversity techniques in order to achieve high quality in signal transmission even in radio communications on fading channels. For example, a radio selective call receiver having a time diversity function has been disclosed in Japanese Patent Unexamined Publication No. 6-334572.
According to the above conventional receiver, when a plurality of signal replicas are received at different arrival times, the absolute value of a sampled signal in a currently received replica is compared with that of the corresponding sampled signal in a previously received replica in symbols, and then one which is greater than the other is selected to produce a resultant sample sequence. Since the sample selection is performed based on the output signal of a detector, the conventional time diversity technique has an advantage that the time diversity is performed without the need of a specific detector for detecting received signal strength.